Apple rolled out its electrocardiogram (ECG) app for the Apple Watch Series 4 yesterday with less fanfare but no fewer questions about how its first wearable consumer heart-monitoring tool will affect healthcare providers.

“The idea that wearables can be used by both patients and their healthcare providers to manage and improve heart health holds promise and should also be approached with caution to ensure information and data are used responsibly and in concert with other evidence-based tools and guidelines,” American College of Cardiology President C. Michael Valentine, MD, said in an Apple release.

To take an ECG similar to a single-lead reading, consumers simply hold their finger on the watch’s digital crown and, after 30 seconds, the heart rhythm is classified as either atrial fibrillation (AF), sinus rhythm, or inconclusive. The waveforms can be stored on an iPhone and shared in a PDF with physicians.

“The role that technology plays in allowing patients to capture meaningful data about what’s happening with their heart, right when it’s happening, like the functionality of an on-demand ECG, could be significant in new clinical care models and shared decision making between people and their healthcare providers,” Nancy Brown, CEO of the American Heart Association, said in the Apple release.

The updated Apple Watch also has a notification feature that checks for signs of AF and alerts the user if it detects an irregular rhythm on five rhythm checks over a minimum of 65 minutes.

Apple acknowledges that in the Apple Heart Study, however, the watch’s AF warning was not confirmed 20% of the time by an ECG patch simultaneously worn by study participants.

Physicians took to Twitter after the app went public yesterday, with Daniel Yazdi, MD, Brigham and Women’s Hospital, Boston, tweeting: “Single lead EKG useful for detecting arrhythmias, not sensitive for ischemia. Excited for this new granularity but benefit/harm of anticoagulation needs to be evaluated.”

Others had a different view. Nishat Siddiqi, MD, University of Aberdeen, United Kingdom, tweeted: “The apple smart watch app for AF is exciting BUT those with the highest risk of AF are older than the average smartwatch user and the false positive rates are too high. So, as a cardiologist, I’ll end up reassuring lots of anxious young people they don’t have AF.”

Michael Katz, MD, @MGKatz036, tweeted, “Of course, as a heart rhythm specialist, I immediately installed the iOS update on Apple Watch to EKGs enabled. We are gonna get wrecked.”

News that the irregular heart rhythm notifications are not intended for people who have been diagnosed with AF also prompted headlines in the Washington Post and groans on Twitter. Electrophysiologist Edward J. Schloss, MD, The Christ Hospital in Cincinnati, tweeted: “Huh? Apple Watch 4 is not designed for the people in which it has the most utility.”

When Apple unveiled the app in September, Medscape Editor-in-Chief Eric Topol, MD, Scripps Research Institute, La Jolla, California, cautioned that the ECG feature could increase the chance of false-positives and detect cases of low-risk AF that don’t need to be treated.

Medscape columnist and electrophysiologist John Mandrola, MD, from Baptist Health, Louisville, Kentucky, said the app could misdiagnose patients because of inaccurate readings or lead to overtreatment of patients. Still, over time, “we may learn important things about arrhythmia from all these data. Similarly, people will gain more health literacy when it comes to their heart rhythm.”

In granting de novo clearance for the new ECG app in less than a month’s time, the US Food and Drug Administration stated that it is not intended for people younger than 22 years, a point that some on Twitter suggested could be easily worked around by changing the watch’s user settings.

When first unveiling the updates this September, Apple Chief Operating Officer Jeff Williams heralded the watch as the “ultimate guardian for your health.”

Apple executives sounded a more moderate tone yesterday.

“Apple Watch has helped so many people around the world and we are humbled that it has become such an important part of our customers’ lives,” Williams said in Apple’s statement. “With the release of these heart features, Apple Watch takes the next step in empowering people with more information about their health.”

Sumbul Desai, MD, Apple’s vice president of health, remarked, “We are confident in the ability of these features to help users have more informed conversations with their physicians. With the ECG app and irregular rhythm notification feature, customers can now better understand aspects of their heart health in a more meaningful way.”

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